The present invention pertains to methods for automatically assembling or collating or singulating of sheets of media such as paper, such as is done by mailing systems when assembling and inserting sheets into envelopes. More particularly, the present invention pertains to controlling the motion of pushers that push sheets through a sheet handling device, such as a mailing machine, a postage meter, an envelope printer or inserter, and including a high-speed inserter.
General Discussion
A typical sheet or envelope handling device includes various structures, motors and sensors. For example, a typical envelope handling device includes an envelope feeding structure for feeding an envelope or a batch of envelopes in singular fashion in a downstream path of travel to a work station. Typical envelope handling devices employ ejection rollers or ejection belts operating at a constant speed, or at some speed that varies as a function of time, speeds chosen so as to avoid envelope collisions and noise, and also to avoid so-called bounce-back from a wall when an envelope strikes a wall designed to stop its forward travel and cause it to drop onto the top of a stack. Depending on how the envelope moves through the device, more or less noise and bounce-back will result. It is beneficial to control to a fine degree the motion of a sheet or envelope handling device so as to keep noise and undesirable motion of the sheets or envelopes to a minimum.
The prior art uses motion profiles to express, as a function of time, the velocity/speed of an axis of a motor that causes motion of a sheet in a mailing system. A motion profile consists of a series of segments, each segment having a duration and each corresponding to a state of motion of an axis of a motor ultimately responsible for imparting motion to a sheet or envelope.
For example, a motor may have an axis that in rotating pulls a sheet through part of a mailing system at a certain speed, after accelerating at a specified acceleration as a function of time, and concluding with some specified deceleration as a function of time. If the sheet does not slip, then the motion of the sheet can be correlated precisely with the motion of the axis of the motor: the sheet moves through the mailing system with a speed that is exactly equal to the speed of rotation of the part of the axis in contact with the sheet, i.e. usually the surface of a belt driven by the axis. In this case, commands are sometimes sent to a motor to impart motion to a sheet for a series of time segments, the commands being based simply on the assumption that the motion of the axis of the motor causing the motion of the sheet can be equated to the motion of the sheet.
On occasion, however, a sheet in a sheet handling device will slip so that the motion of the axis does not necessarily indicate the motion of a sheet (or envelope). Then the motion of an axis of a motor can be conditioned based on receiving commands from sensors used to detect the presence of the sheet as it moves through the sheet handling device.
Whether commands are sent based on a sheet not slipping, or based on information from sensors, the commands can be sent without regard to, i.e. independent of, the motion of the axis of any other motor. It is also possible, however, to send commands to a motor based on the motion of other motors.
The sending of commands to a motor based on the motion of (the axis) of another motor (which motion can be based on the motion of still a third motor, and so on), was in the past accomplished using mechanical gearing. Today, motors can be made to communicate electronically and use what is now sometimes referred to as electronic gearing, but also known as displacement mapping, in which the motion of the axis of one motor is expressed in terms depending only on the motion of the axis of another motor, whether or not there is slippage.
Problem in Synchronizing an Insertion Engine to a Collating Transport for a High-speed Inserting Machine
Motion control according to the above-described techniques is advantageously used in synchronizing an insertion engine to a collating transport for a high-speed inserting machine, i.e. in a high-speed inserter that gathers sheets to be inserted into an envelope and then inserts the collation (gathered sheets) into the envelope. The combined operations of gathering the sheets of a collation and then inserting the collation into an envelope must be precisely coordinated (at least in the case of a high-speed inserting machine) so as not to wrinkle the sheets in the transition from gathering to inserting, or to lose control of the collation in the act of inserting the collation into the envelope, such as for example by a premature deceleration of a pusher forcing the collation into the envelope. The gathering of the sheets of a collation is performed by what is called a collating transport, including a motor driving a belt with a pusher attached to the belt, and the inserting of a collation into an envelope is performed by what is here called an insertion engine, including various components and in particular an overhead pusher transport which in turn includes a motor driving a belt with an attached pusher.
What is needed is a methodology for providing motion profiles that express the required motion of the axis of the collating transport motor and also that of the insertion engine so as to precisely coordinate the motion of the two axes and so as to maintain control over the collation throughout the insertion process.
Accordingly, the present invention provides a method for dynamically determining a motion control profile used in controlling motion of an axis of an overhead transport motor so as to be synchronized to the motion of a collating transport motor of an insertion engine used to insert a collation into an envelope when the collating transport motor causes a collating pusher to handoff the collation to an overhead pusher being driven by the overhead transport motor, the motion profile consisting of a finite number of segments and repeating after the finite number of segments, the finite number of segments constituting a cycle, the method including the steps of: electronically gearing the overhead transport motor to the collating transport motor from the beginning of a cycle until handoff; based on position information provided by a sensor, determining whether the collating transport is decelerating between handoff and insertion; and using either forward integration or electronic gearing of the overhead transport motor to the collating transport motor up until the collating transport motor is first determined to be decelerating between handoff and insertion, and using forward integration when the collating transport motor is first determined to be decelerating between handoff and insertion and continuing the forward integration until insertion.
In a further aspect of the invention, the forward integration is used when the collating transport motor is first determined to be decelerating between handoff and insertion and continuing the forward integration until the end of the cycle.
In another further aspect of the invention, the electronic gearing is used from insertion until the end of the cycle.